Customize image build and integration test

[msftcoderdjw]

Changes:

1. Based on the review requirements, we need to use different base images to generate Symphony-api and Symphony-k8s for Azure builds. So include base image ARG in dockerfile and provider override mage utility functions.
2. Provide ways to customize integration tests.
3. Fix typos and unused imagePrivateRegistryUrl.

[Haishi2016]

How do we produce a non-Microsoft release now? We need to keep in mind that this is still an OSS repo that is supposed to remain Microsoft neutral.

[msftcoderdjw]

How do we produce a non-Microsoft release now? We need to keep in mind that this is still an OSS repo that is supposed to remain Microsoft neutral.

For non-Microsoft release, we still rely on https://github.com/eclipse-symphony/symphony/actions/workflows/release.yaml to generate build. Yes, we are trying to keep OSS repo Microsoft neutral so we add arguments to Dockerfile instead of just check in the base images. We will override the required base images in downstream projects build.